Cut each plantain into two halves and each half into three strips.
Heat vegetable oil in a large skillet over medium-high heat. Gently lay plantain strips into hot oil; drizzle vanilla extract over plantains and season with cinnamon. Place a cover on the skillet and cook the plantains until browned completely, 5 to 7 minutes per side. Transfer plantains to a plate lined with paper towel to drain; sprinkle sugar over the plantains.